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use of OpenCV Library with DirectShow on Visual C++ .Net 2003 enviroment

Posted on 2006-06-13
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Hello,
Im trying to write a motion detection algorithm with my camera by using OpenCV graphic library. My camera unit actually is running through a video capture card and OpenCV lib does not provide that kind of camera sistem. As my understanding, only way to utilize OpenCV is using DirectShow. I found a web site "http://www.site.uottawa.ca/~laganier/tutorial/opencv+directshow/cvision.htm" which is about both openCV and directShow but all represented code examples were written in Visual C++ 6.0. I tried lots of way to convert examples into Visual C++ NET 2003 using managed c++, but i didnt.

So, can you help me to write this code in managed c++ or can you show me to way how to use OpenCV library with DirectShow.
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Question by:ebnhuseyin
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fffej78 earned 750 total points
ID: 16900185
http://sourceforge.net/projects/directshownet/ might be of some help (it's a .NET binding for DirectShow).

As someone who has worked with DirectShow, I can tell you it' sgoing to be a huge pain in the butt to get OpenCV and DirectShow interacting with .NET.  The best option would be to buy the Visual C++ that doesn't spew out managed code, it might cost $100 or so, but it'll stop you getting a massive headache.

You'll need to write a series of DirectShow filters.  Your best starting point is:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/directshow/htm/writingdirectshowfilters.asp

If you are lucky, then your camera already has a DirectShow filter and you just need to build the appropriate graph

http://msdn.microsoft.com/library/en-us/directshow/htm/capturegraphbuilder.asp?frame=true

So you'll grab a frame from the camera, do something and then send it upstream to a renderer.  You'll have to implement the "do something" filter yourself.  It'll take an image as input, and return an image as output.  Not sure what your algorithm does, maybe it highlights what is moving in the image.  

Check out http://www.hmelyoff.com/index.php?section=12 for some example motion detecting filters.  You should at least be able to use this to verify you have the general idea of things in the graph builder thing that you get with the DirectShow SDK.
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by:e_tadeu
ID: 16904735
Why do you want to use managed (.net/clr/interpreted) code, when you have the faster native API's? Just use the DirectX SDK and OpenCV directly on C++ :)
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by:mrblue
ID: 16906299
I think that the easiest way is to modify sample transform filter from DirectX SDK (for example <dxdir>\C++\DirectShow\Filters\Gargle).

You will have to modify "Transform()" method in the simplest case. Note that this filter derives from CTransInPlaceFilter what means it transforms data in-place. If you want to change frame format you will have to inherit from CTransformFilter.

Likely you will also have to modify CheckInputType.
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by:fffej78
ID: 16906571
To follow up with mrblue, I don't think you will be able to compile DirectShow filters as "managed C++", then need to be built using standard C++ as they are exposed as COM objects.
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by:mrblue
ID: 16906787
I far as I know .NET compiler supports also unmanaged code so at least compiling should't be a problem (correct me if I'm wrong).
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by:ebnhuseyin
ID: 16908925
thanks guy for the answers. Actually my idiea to use managed c++, i thought to write event base application with opencv on NET platform. But when t tried to use source code which links is given above, i coudnt converted it into managed C++. Everything was written with old code system. Header files always were giving syntax error anyway.
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